Help again please Don’t get it at all

Kevin has just finished paying off his loan. he was assessed a service charge of $422. he paid off the principal and the interest by making weekly payments of $36.13 for four years. if the principal was $7,150, how much did kevin pay in finance charges, to the nearest dollar? a. $498 b. $365 c. $422 d. $787

Add the two expressions 3.8b - 7 and 2.9b + 9 enter your answer in simplified form

Witch represents the inverse of the function f(x)=1/4x-12